The 58-year-old victim said he had gone upstairs at closing time at the Lancashire pub where he was attacked and tied up by four men carrying knives and wearing balaclavas.
Following the assault, in which the victim received an eye injury and suspected broken ribs, he described the men as having Merseyside accents. They stole money before running off.
After managing to free himself, the licensee ran to the nearby White Bull pub across the street for help and was taken to Blackpool Victoria Hospital for treatment.
No one else was in the pub at the time of the incident.
Detective Inspector Lee Wilson of Blackpool CID said: “This was a vicious robbery carried out by men who clearly had no hesitation in using extreme levels of violence to get what they wanted.
“I would appeal to anyone who saw anything suspicious at the time, or any people or vehicles acting suspiciously in the days before the robbery, and anyone who has any information about who these offenders could be, to get in touch with us.”
Anyone with information is asked to contact Lancashire Police on 101 quoting log number 0063 of 31 May or the confidential Crimestoppers line on 0800 555 111 or online at crimestoppers.org.